The H.323 standard of the International Telecommunication Union (ITU) specifies signalling and transport for multimedia traffic over a packet switched network. Another protocol that addresses this same issues as the H.323 standard is referred to as SIP (Session Initiation Protocol) standard.
Network solutions according to H.323 and SIP mainly and typically support multimedia communication between end-points that by some means are connected to a packet-based network, such as for instance an IP (Internet Protocol) network. Networks and end-points that support H.323 or SIP (or, are given this support via other means, such as e.g. an H.323 or SIP enabled gateway), can provide services and functions as can be found in a typical PSTN (Public Switched Telephone Network). Accordingly, depending on the capabilities of the end-point, such networks can support and provide to a user more than plain voice communication. Other examples of supported communication types are video, fax, data sharing, information services, etc.
Telecommunication solutions according to H.323 or SIP will typically support the same type of services as those provided by a normal PSTN. Such services are call forwarding, call waiting, call screening, etc. Because H.323 and SIP telecommunication solutions are using new network architectures, such as e.g. based on IP, and have support for smarter end-points than PSTN, a new sets of services will be supported in those networks.
Although H.323 and SIP are new protocols, telecommunication solutions according to those protocols will encounter problems with regard to service interaction similar to those experienced in the PSTN. A reason for the occurrence of a service interaction problem is that some services are invoked when an end-user establishes a call. This means that services are applied after some of the routing of a call is already done, which in turn can lead to adverse interaction of a service or services.
In the following and with reference to the accompanying FIG. 1, a typical known service solution in a typical telecommunication network, as will be readily appreciated by a person skilled in the art, will be explained by way of a model description.
In FIG. 1 the normal network model is shown. It should be noted that the reference numerals only give an indication on the normal or typical call path flow, as other call path scenarios also are known to exist:
1: The services are configured by a network operator and potentially also by an end user
2: The call is triggered at the user side and signalling handler on the user side communicates with the signalling handler on the network side
3: The service executor is invoked
4: The service executor communicates with the service configuration part in order to download information on e.g. available services
5: The service executor returns service information to the signalling handler, that might be ordinary PSTN services like CLIP (Calling Line Identity Presentation)/CLIR (Calling Line Identity Restriction), PNP (Private Numbering Plan), OCB (Outgoing Call Barring) etc.
6: The signalling flow can be “flooded” to the terminating side (the “reflected side”)
7: When the signalling part is executed, information on which media channels to set up are passed over to the media generator.
Accordingly, the media is set up through the network. Note that media and signalling usually do not follow the same paths. Note also that the “reflection plane” indicated in FIG. 1 illustrates that the originating side may or may not see a “mirrored” or “reflected” terminating side that is similar to the originating side.
The service configuration and service executor shown in FIG. 1 can also exist on the user side. The advantage of having the service configuration and service executor on the network side is that the operator is given fill control over the service environment and all possible interactions between services.
U.S. Pat. No. 5,822,419 to Enstone, et al., discloses a method of detecting interactions between services in a set of services in a telecommunications system. A service abstract is produced based on a Basic Call State Model (BCSM) which gives a high level description of a Call Processing Subsystem and a data processing sequence performed by basic call processing and by the services in respect of a global data item. For detecting service interactions, a service abstract is produced based on a Basic Call State Model and a data processing sequence performed by basic call state processing and by the services in respect of a global data item.
European Patent publication no. EP0825787 to British Telecomm (GB) discloses, in a connection management system for setting up connections in a communications network, run-time negotiation is carried out to avoid feature interaction. Users of the network are provided with user agents (intelligent software) who have access to user profiles. When a calling user wants to set up a particular connection configuration, which may involve service features such as ring back later on busy, their user agent sends a connection configuration proposal to the user agent or a called user. The two user agents then negotiate to establish a mutually acceptable connection configuration, if one is available. The negotiation is based on alternative connection configurations stored in order of preference in the respective user profiles. These are proposed and counter-proposed by the user agents in descending preference order until the mutually acceptable configuration is reached or the connection fails.
Patent publication no. WO9750232 to Bell Communications Res (US) discloses a method for managing communications between a service origination node and a plurality of serving nodes where the serving nodes are simultaneously active for a particular trigger to thereby generate a reply to the service origination node. The method includes the step of determining control options for each trigger indicative of service categories by capturing service interaction principles supplied by a serving node services expert acting as a mentor. The service interaction principles are based upon a requirement of executing service categories in each of the serving nodes for each trigger. The method also includes the step of controlling execution of each of the service nodes and the service categories for the particular trigger with reference to the control options to generate the reply.
Patent publication no WO9429993 to TELEFON AB L M ERICSSON (SE), discloses a method of avoiding undesirable interferences between services in a telecommunications system that includes basic software for a basic service and supplemental software for services supplemental to the basic service. The supplemental software is divided into action software, which acts solely on the basic service, and supplemental software, which acts on the remaining supplemental software. A supplemental service is represented by action elements. Combinations of action elements form nodes in a mathematical binomial tree. Only those combinations, which correspond to interference, i.e., an undesirable behaviour, between supplemental services will form a number of structures, called interference event trees. Before a supplemental service can be executed, its action elements are compared with nodes in the interference event trees, with the intention of ascertaining whether or not the former coincide with action elements belonging to the nodes in the latter. Only those interference event nodes whose sets of action elements are equivalent with the set of action elements of the supplemental service or a set thereof are selected. An interference event node whose set of action elements is a subset of the action elements of a node that has already been chosen cannot be selected. Interaction software belonging to selected nodes in the interference event trees is added to the basic software.
It is an object of the invention to provide an improved solution in a modem telecommunication network for mitigation of service interaction or service conflict problems that may occur when conflicting services pertinent to a subscriber are invoked.
It is a further object of the invention to provide an improved solution in a modem telecommunication network for mitigation of network load problems resulting from service interaction or service conflict problems.